Architectural designs including unique or complex ornamentation have long been favored by architects and builders. For example, medieval cathedrals having complex ornamentation were hand crafted, using concrete or other suitable material that was laboriously formed into the desired shape.
In more modern times, building materials such as dry wall, plywood, and particle board have supplemented concrete and other cementitious materials. However, these newer materials are also quite difficult to form into unique or complex shapes. Moreover, these materials are of flat construction so that they cannot be used where three dimensional ornamentation calls for substantial depth.
When expanded polystyrene (EPS) was first invented, it was thought to have no utility in the construction industry because early EPS was quite soft and breakable; accordingly, it was used as a shock-absorbing packaging material and as a container within more durable containers.
However, builders noticed that it could easily be cut or molded into different shapes, so experiments began to determine whether or not it could be used to provide the ornamentation so difficult to achieve with cementitious materials, plywood and the like. The experimentation was extensive, because builders realized that if EPS proved suitable for use in ornamentation work, experienced and expensive carpenters and brickmasons would no longer be needed to create the free-form shapes so often prescribed by architects.
The results were unsatisfactory EPS, as expected, was too pliable to serve as a building material. It was light in weight and easy to install, but even the most routine contact damaged it. For example, a homeowner leaning a ladder against a house to gain access to the roof could destroy an EPS window ornamentation just by inadvertently bumping it with the ladder. In addition, EPS was found to be highly susceptible to damage caused by the ultraviolet rays of the sun.
EPS was so much easier to make into free forms and was so easy to work with and lowered the builder's costs so much, however, that it was not abandoned after the early disappointing trials. Instead, researchers began to look for ways to strengthen it so that it could withstand the bumps and abuses that any building material must withstand and to look for coatings that would protect it from ultraviolet damage.
The conventional wisdom was that, despite its lack of durability, EPS could somehow be strengthened and protected and its advantages and cost savings could therefore be realized.
However, before the invention of the process disclosed hereinafter, EPS has persisted in disappointing architects, builders and owners alike. Strengthening processes have been developed, but these processes have several drawbacks. For example, strengthening EPS has had the undesirable side effect of destroying the detailed ornamentation cut into the EPS.
The destruction of detail occurred because inventors increased the durability of EPS by coating it with a protective layer of concrete or stucco. It was found, however, that a standard concrete or stucco mix would not bond satisfactorily to EPS, but would tend to crack off even under light impact. Inventors then developed bonding agents made from latex or acrylic plastic resins, but even this relatively thin layer of cementitious material erased the shallow valleys of the underlying ornamental design cut into the EPS.
A further refinement was the mixing of these bonding and strengthening agents with a cement mixture to produce cementitious coatings that were stronger and bonded well with EPS. This significant new building process utilizing EPS was then developed. These coatings could be relatively thin and easy to apply by trowelling or spraying and when used with reinforcing mesh were proven to be adequately durable and provided sufficient protection to the EPS. This building system then became generally acceptable in the construction industry.
The current state of the art method for applying this cementitious system is to bond sheets of open mesh to the EPS. This can be accomplished by first trowelling the mesh in place with a primary or first coat of cementitious coating, or the mesh can be treated at the factory with a contract cement or even applied with a compatible adhesive at the job site. A primary coat of cementitious material, however, is needed to properly bond the EPS and the mesh which has to be fully embedded to protect it from ultraviolet damage to fully hide it prior to finishing. A second or finish coat is then applied, said coat can be cementitious with color added, or simply a compatible paint.
Although the resulting product is strong and thinner than a concrete system, this method still destroys the subtle details of ornamental design unless a considerable amount of hand labor is used to redefine the original design cut into the EPS. This can only be accomplished by carefully placing the mesh in direct relationship to the design and embedding the cementitious material so that it fully covers the mesh. This process is very labor intensive and expensive.
The art accordingly has reached an apparent impasse. Coatings that impart adequate durability to the EPS reduce its utility as an ornamental building structural element, and coatings that preserve at least some of its utility as an ornamental material are labor intensive and not cost effective
It is apparent that the solution to this quandary is not obvious, in view of the prior art, to lay persons or to those of ordinary skill in the EPS and construction industries.
There is still another problem that plagues the industry as well. Once the EPS has been cut into shape at the factory, it must then be transported to the job site and attached to the house, apartment, office building or other structure under construction. Currently, adhesives and special large face mechanical fasteners are used to attach and hold the EPS in place. This attachment process is labor intensive. Moreover, the fasteners are expensive and the large face of the fastener pulls down into the soft foam. This then requires that the void created in the surface of the EPS be filled with a patching process.
Furthermore, as mentioned above, the layers of cementitious material to be trowelled or sprayed onto the EPS at the job site must be mixed at the construction site. Typically, the cementitious product is prepared by mixing a gallon of resin with a ninety four pound bag of concrete and one hundred fifty pounds of sand and adding water to obtain the desired consistency. This on site preparation of materials and subsequent application onto the EPS is a slow and costly process.
Nevertheless, it is still easier to cut a block of EPS into a desired ornamental shape at a factory, to transport that block of EPS to the job site, and to complete the above-described process than it is to construct ornamental elements by any other heretofore known method. Accordingly, even though the state of the art is not entirely satisfactory, the above-described cementitious covered EPS material is in widespread use by the construction industry.
Innovation in this field is clearly needed, but the teachings and suggestions of the art provide no clues as to what should be done.